Pulling clamp for continuous rod or coiled tubing strings

ABSTRACT

A pulling clamp is provided for releasable connection to a blunt, uphole string end of a continuous string. A main clamp body has clamp bore therethrough and having a string-receiving opening at the pulling end for receiving the string end, an actuating bore at the pulled end and a tapered bore therebetween. A taper insert having a radially compressible gripping bore is locatable in the tapered bore and axially actuable between a passive first receiving position, for receiving the string end, and the active second gripping position for radially compressing the taper insert about the string end for actively gripping the string end therein. The taper insert can be axially actuated using a threaded main body and threaded top cap for sandwiching the taper insert therebetween, the top cap being threaded axially into and out of the pulled end of the main body between the passive and active positions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a regular application claiming priority of U.S. provisional application 61/532,348, filed Sep. 8, 2011, the entirety of which is incorporated herein by reference.

FIELD

Embodiments herein are related to apparatus used for temporarily engaging a blunt end of a string of coiled or continuous rod or tubing, and more particularly, to apparatus or clamps used for connecting between the string and apparatus for lifting and lowering the string in and out of a wellbore, such as during a servicing operation.

BACKGROUND

Downhole pumping operations in the oil and gas industry have used, and many still use, a string of a plurality of sucker rods for operating downhole pumps situate in wellbores accessing oil and gas formations. The sucker rods themselves are typically fit with male and female threaded connections formed with upset ends. For installation, retrieval and service operations, the threaded and upset ends are also used to aid in handling the individual rods including engaging the upset ends for supporting the combined weight of the string.

The oil and gas industry has also become familiar with the use of continuous or coiled rod and coiled tubing for operating wellbore pumps and performing service operations. The continuous rod and coiled tubing are typical of such continuous strings in that they are usually dispensed from a supply, run through a wellhead into a wellbore to depth, suspended in the wellbore and cut off above the wellhead. A single, continuous rod is conventionally often used to replace a plurality of sucker rods for rotary drive of a progressive cavity pump or PC pump. The continuous rod is rotatably supported at the wellhead, such as by a rod clamp, and is rotatably connected and driven from a rotary drive at surface. Coiled tubing is used for many different services, including for accessing the wellbore for support of a downhole tool and communication of fluid between the tool and surface. As with continuous rod, coiled tubing is typically supported at surface, such as by a blowout preventer at the wellhead, and cut off thereabove for connection to fluid devices.

The ability to cut off a continuous string at any point intermediate its length is one advantage but also results in a string termination or blunt end which is more cumbersome to later attach to for service operations, namely being absent a designed upset or machined end for the gripping or mechanical attachment of conventional service tools.

Particularly, in the case of continuous rod drive systems for downhole tools, such as progressive cavity pumps, such as described in Applicant's co-pending applications, U.S. published application 2011-0266005-A1, Canadian published application 2,738,500 and PCT published application WO2011/134085A1, a cut blunt end of the continuous rod string extends above the drive head, but provides no convenient and secure point of attachment for the attachment by lifting apparatus. During lifting, lowering and supporting of the continuous rod string, such as for pulling the rod string and pump from the wellbore or for pulling the pump's rotor from the pump's stator such as for cleaning the pump, means are required to engage the cut end of the rod string.

It is known in the prior art to weld on a coupling for threaded attachment or to apply a clamshell clamp for gripping about a blunt end of a continuous string, such as where welding on-site may be dangerous. One example is a Hunting Welltronic tool/tubing clamp as provided by Hunting Welltronic Ltd., of Aberdeen, Scotland. As described, the Hunting Welltronic tool/tubing clamp is

-   -   a “device used for securing coiled tubing tools during         deployment operations. It can also be utilized to secure Coiled         Tubing while being fed off of the reel or being lifted up out of         the hole or out of the well. The tool/tubing Clamp comprises of         two halves which contain slip segments to suit a specific         tool/tubing diameters. A tapered bowl ensures the slip grips the         tool/tubing in one direction and allows the tool/tubing to slip         in the other. The spacer plates retain the slips as well as         prevent the clamp from damaging the tool/tubing when the         clamping bolt is engaged. The Tubing Clamp can be supplied with         a range of slips to suit various tool/tubing diameters.”

The prior art clamp is quite substantive is size and can interfere with surface equipment including a pump drive head. Alteration of the blunt end for convenience of connection or other purpose can have adverse ramifications for surface equipment including drives and stuffing boxes.

Clearly there is a need for reliable, safe means for engaging connecting continuous or coiled rod and coiled tubing to tools, such as conventional service tools including lifting and lowering apparatus, without the problems associated with prior art clamps.

SUMMARY

A pulling clamp is provided for releasable connection to a blunt, uphole string end of a continuous string. The pulling clamp can form an upset for engagement with lifting apparatus. Alternatively, the pulling clamp incorporates a pulling connection for connection to lifting-specific components or a pony rod having a conventional lifting end for engagement with the lifting apparatus.

In one embodiment, the pulling clamp comprises a main body having a bore for releasably gripping the string end and provides a lower pulling end. The main body itself forms an upset, the pulling end engageable by lifting apparatus.

In embodiments, the main body has a lower pulling end and an upper pulled end, the main body having a clamp bore formed therethrough, the clamp bore comprising a string-receiving opening at the pulling end for receiving the string end, an actuating bore at the pulled end and a tapered bore therebetween. A taper insert having a compressible gripping bore is provided and locatable in the tapered bore. A top cap is engageable with the actuating bore, the top cap being axially movable between passive and active positions to actuate the taper insert between a first receiving position and second gripping position respectively, wherein in the first receiving position, the gripping bore receives the string end and is passively uncompressed thereabout; and in the second gripping position, the top cap axially engages the taper insert for driving the taper insert axially into the tapered bore for radially compressing the taper insert about the string end for actively gripping the string end therein.

In another embodiment, the actuating bore is threaded and the top cap is threaded for threading axially into and out of the pulled end of the main body between the passive and active positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of an arrangement of a top drive for rotary drive of a progressive cavity pump including a drive clamp according to the prior art for suspending and rotatably coupling the continuous rod to the top drive and an embodiment of a pulling clamp releasably connected to a cut end of the continuous rod;

FIG. 1B illustrates direct pulling of the pulling clamp by an elevator;

FIG. 2A is a plan view of the pulling clamp according to FIG. 1A;

FIG. 2B is a cross-sectional view of the pulling clamp along A-A of FIG. 2A;

FIG. 3 is a perspective view of the pulling clamp according to FIG. 1A;

FIGS. 4A to 4C are perspective views of exploded components of the pulling clamp as shown in FIG. 3, more particularly

-   -   FIG. 4A is a perspective view of a top cap;     -   FIG. 4B is a perspective view of a taper insert;     -   FIG. 4C is a perspective view of a main body of the pulling         clamp; and     -   FIG. 4D is a perspective view of a jam nut;

FIG. 5A is a cross-sectional view of the pulling clamp according to FIG. 3, illustrating the relationship between the components of FIGS. 4A-4D when assembled;

FIG. 5B is a side view of the pulling clamp according to FIG. 5A;

FIG. 6 is a partially sectioned perspective view, according to FIG. 5A, illustrating the positioning of the taper insert within the main body of the pulling clamp, the taper insert shown in full engaged in the tapered bore;

FIG. 7 is a perspective view according to FIGS. 2B and 5A;

FIGS. 8A to 8D are detailed views of the top cap according to FIG. 4A and more particularly,

-   -   FIG. 8A is a side view illustrating internal threading of the         top cap in dotted lines;     -   FIG. 8B is a plan view according to FIG. 8A;     -   FIG. 8C is a side view according to FIG. 8A, the internal         threading in dotted lines being removed for clarity; and     -   FIG. 8D is a plan view according to FIG. 8C;

FIGS. 9A to 9D are detailed views of the jam nut according to FIG. 4B and more particularly,

-   -   FIG. 9A is a side view illustrating internal threading of the         jam nut in dotted lines;     -   FIG. 9B is a plan view according to FIG. 9A;     -   FIG. 9C is a side view according to FIG. 9A, the internal         threading in dotted lines being removed for clarity; and     -   FIG. 9D is a plan view according to FIG. 9C;

FIGS. 10A to 10D are detailed views of the taper insert according to FIG. 4C and more particularly,

-   -   FIG. 10A is a side view illustrating wickers within a bore of         the taper insert in dotted lines;     -   FIG. 10B is a plan view according to FIG. 10A;     -   FIG. 10C is a side view according to FIG. 10A, the internal         threading in dotted lines being removed for clarity; and     -   FIG. 10D is a plan view according to FIG. 10C;

FIGS. 11A to 11D are detailed views of the main body according to FIG. 4D and more particularly,

-   -   FIG. 11A is a side view illustrating internal threading of the         main body in dotted lines;     -   FIG. 11B is a plan view according to FIG. 11A;     -   FIG. 11C is a side view according to FIG. 11A, the internal         threading in dotted lines being removed for clarity; and     -   FIG. 11D is a plan view according to FIG. 11C;

FIGS. 12A to 14C illustrate steps in a process of engaging embodiments of the pulling clamp according to FIG. 3 with a cut end of continuous rod, more particularly;

-   -   FIG. 12A is a side view of the pulling clamp, illustrating         internal threading and components in dotted lines, the cut end         of the continuous rod being inserted into the main body through         the taper insert and bottoming out at the top cap;     -   FIG. 12B is a side view according to FIG. 12A, the dotted lines         illustrating internal threading and components having been         removed;     -   FIG. 13A is a side view of the pulling clamp according to FIG.         12A, the top cap being tightened to compress the taper insert         about the cut end;     -   FIG. 13B is a side view according to FIG. 13A, the dotted lines         illustrating internal threading and components having been         removed;     -   FIG. 13C is a fanciful perspective view according to FIG. 13B,         wrenches shown engaging the main body to illustrate preventing         rotation thereof while the top cap is being rotated to tighten;     -   FIG. 14A is a side view of the pulling clamp according to FIG.         13A, the jam nut being tightened against the main body to lock         the top cap against rotation;     -   FIG. 14B is a side view according to FIG. 14A, the dotted lines         illustrating internal threading and components having been         removed; and     -   FIG. 14C is a fanciful perspective view according to FIG. 14B, a         wrench shown engaging the jam nut to indicate rotation of the         jam nut; and

FIG. 15 is a sectional view of a coiled tubing installation in which embodiments of the pulling clamp are incorporated for servicing of the installation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments disclosed herein provide a multi-component pulling clamp 10 for releasable connection to a cut or blunt end of a continuous rod or tubing string without alteration of the blunt end, referred to herein as the string end.

Embodiments are particularly useful for continuous rod drive systems for downhole tools, such as progressive cavity pumps as described in Applicant's co-pending applications, U.S. published application 2011-0266005-A1, Canadian published application 2,738,500 and PCT published application WO2011/134085A1, incorporated herein by reference in their entirety.

Herein, embodiments of the pulling clamp 10 are often described in the context of continuous rod having a solid, circular cross-section however other continuous string including coil tubing having tubular yet circular cross-sections are contemplated.

In an embodiment, the pulling clamp is incorporated into a continuous rod pumping system having a surface-accessible, string end and for enabling servicing of the continuous string without substantial modification of the string end. Such a rod-driven pumping system can comprise a drive positioned at surface, a continuous rod driveably connected to the drive and extending downhole through a bore of a production tubing to a pump, forming a production annulus therebetween, and a coupling connecting between the continuous rod and the pump. In an embodiment, the rod-driven pumping system is a rod-driven progressing cavity pump having a stator and a rotor operatively engaged within the stator for rotation therein. The drive comprises a drive head having a hollow drive shaft supported on a wellhead at surface. The continuous rod is driveably connected through the hollow drive shaft of the drive head. The continuous rod is connected at a downhole end through a coupling to the rotor.

The continuous string extends through the drive and remains unadulterated for servicing of the drive head thereover, including a stuffing box as applicable. The string end is truncated to form a cylindrical end which is unadulterated, having substantially the circular cross-section and cylindrical dimensions of the remainder of the continuous string extending therebelow.

In another embodiment, a continuous string is provided for driving a pump in a wellbore, the continuous string having an uphole end for drivingly connecting to a drive at surface and a downhole end for connection to the pump such as through a coupling. Again, the uphole end is truncated to form a cylindrical string end which is unadulterated, having substantially the cylindrical dimensions as that of the remainder of the continuous rod extending therebelow. The string end is accessible at surface for connection to an embodiment of a pulling clamp as set forth herein.

Accordingly, an embodiment of the pulling clamp described herein can be applied for temporarily connecting to and suspending the continuous string in production tubing. The pulling clamp can be connected to structure for implementing lifting or pulling of the continuous string. In an embodiment the pulling clamp forms part of an elevator system for temporary and releasable connection to a service rig, crane or other lifting apparatus.

FIG. 1A illustrates an arrangement of a top drive 1 for rotary drive of a progressive cavity pump (PC pump). A continuous string 2 of continuous rod, such as COROD® (Trademark of Weatherford/Lamb, Inc.) extends through a wellhead 4 for connection to and driving the PC pump. The continuous string 2 has a generally cylindrical cut end, referred to herein as a string end 6. A drive clamp 8, according to the prior art, suspends the continuous string 2 in the wellbore and rotatably couples the driven string 2 to the top drive 1. For manipulation of the string end 6, such as for servicing the string 2, the well or the downhole tool or pump, an embodiment of a pulling clamp 10 is releasably connectable to the string end 6.

The pulling clamp 10 is an easy to use, yet large lifting capacity device having a narrow profile, sufficient to be fit and actuated in close quarters, such as that shown in FIG. 1A where the wellhead centerline C is in close proximity to the top drive 1.

The pulling clamp 10 can form an upset directly engageable with the components of lifting apparatus, or can incorporate a pulling connection engageable with the lifting apparatus. The pulling connection, such as an elevator 12 can be connected directly to the pulling clamp 10 or can be connected thereto through an intermediate apparatus 14, such as a length of pony or sucker rod. As shown, the pony rod 14 is provided, at a first end 16, with the elevator 12 for connection to a hook of the lifting apparatus. In the shown embodiment, the pony rod 14 is threadably connected at a pulling connector 18 of the pulling clamp 10 for connection to the string end 6.

As shown in FIGS. 2A and 2B, an embodiment of the pulling clamp 10 engages the string end 6 for providing a releasable connection between the continuous string 2 and some lifting or pulling apparatus, such as a service rig.

In greater detail and having reference to FIGS. 2B to 7 and FIGS. 11A to 11D, the pulling clamp 10 comprises a main body 20 having a string-receiving opening or bore 22 at a pulling end 24 for receiving the string end 6 of the continuous string 2 and an internal tapered bore section 26 thereabove.

As shown in FIGS. 2B, 4B, 5A, 6, 7, and 10A to 10D, a taper insert 28 is provided for positioning within the tapered bore 26, the taper insert 28 having a gripping bore 30 for receiving the string end 6 and axially operable within the main body's taper bore 26 for releasably and radially compressing the taper insert 28 for gripping the string end 6 therein. The gripping bore 30 is radially compressible from an open, receiving position, for axially receiving the string end 6 to a gripping position. In the gripping position, the gripping bore 30 is compressible to a diameter being smaller than a diameter of the string end 6 to be gripped.

A top cap 32 is provided and is axially movable into an actuating bore 34 at pulled end 36 of the main body 30, the actuating bore 34 being in communication with the tapered bore 26 therebelow.

The top cap 32 is operable between two positions; movable between passive and active positions to actuate the taper insert between a first receiving position and second gripping position respectively. In the receiving position, the top cap 42 is released sufficiently from the taper insert 28 to actuate the gripping bore to an receiving position. In the gripping position, the top cap 32 is movable axially into the actuating bore 34 for engaging the taper insert 28 and driving the taper insert 28 axially into the tapered bore 26 of the main body 30. Tapered interface or the taper insert 28 and tapered bore 30 cooperate to radially compress the taper insert 28 and the gripping bore 30 to the gripping position for gripping the string end 6 therein.

In an embodiment, the top cap 32 is fit with an internal threaded pulling bore 37 at a top free end 38 of the top cap 32 for engagement with the pulling connection such as through the pony rod 14, as discussed above.

Alternatively, as shown in FIG. 1B, the pulling clamp itself 10 forms a releasable upset which can be releasably coupled to the blunt string end, an elevator 12 engaging the pulling clamp directly such as about the pulling claim 10 or directly below the main body 20.

In the gripping position, axial pulling load of the continuous string 2 is transferred through the taper insert 28 and to the main body 20 by virtue of the taper insert not being able to exit through the string-receiving opening. In the case using a top cap connection, the load is transferred through the top cap 32 to the lifting apparatus.

In greater detail, the taper insert 28 is actuated by axial movement of the taper insert 28 along the taper bore 26. The taper insert 28 has a driven shoulder 40 and the top cap 32 has a lower driving shoulder 42.

As shown, in this embodiment, axial movement is through threaded movement of the top cap 32 in an internally threaded bore 34. The axial movement moves the driving shoulder 42 axially along the main body 20. Tightening threaded movement engages the top cap's driving shoulder 42 with the taper insert driven shoulder 40 for actuating the taper insert 28 to move axially within the taper bore 26, radially compressing the gripping bore 30 about the string end 6. The structure of the main body 20 is robust and resists the expansive forces thereon imposed by the tapered interface between the taper insert 28 and the taper bore 26. In the gripping position, the string-receiving bore or opening 22 has an effective diameter which is smaller than a combined diameter of the gripping taper insert 26 and string end 6 to avoid pull through at string lifting weights.

The taper insert 28 may have an initial gripping bore diameter about that of the string end 6. The gripping bore 30 may flex radially to receive the diameter of the string end 6. Alternatively, the initial gripping bore diameter may be slightly oversized to loosely to receive the diameter of the string end 6.

In an embodiment, the taper insert 28 is manufactured with an elastic radial compressible range permitting the gripping bore 30 to open, as necessary, to a diameter about that of the string end 6 in the released position and to radial compress to the effective gripping diameter, in the gripping position. The pulling clamp 10 is reusable. One may replace the taper insert 28 each use or the taper insert 28 is also reusable. In an embodiment, the taper insert 28 has an elastic compressible range to permit the radial compression and a radial release between the first released position and second gripping position.

In embodiments, having reference to FIGS. 2B, 3, 4D, 5A-7 and 9A-9D, and where the top cap and main body are threadably coupled, locking means or lock such as a jam nut 50 is provided to lock the top cap 32 into position, such as in the gripping position to prevent premature release of the top cap 32 from driving engagement with the taper insert 28.

The top cap 32 has head 52 at the free end 38 and a smaller diameter externally threaded portion 54 which extends below for threading into the internally threaded bore 34 of the pulled end 36 of the main body 20. The top cap external threaded portion 54 has a length greater than that of the main body's internally threaded bore 34 sufficient to threadedly install the jam nut 50 therebetween. When the top cap 32 is tightened to fully actuate the taper insert 28 to the gripping position, there is sufficient axial clearance between the top cap 32 and a locking shoulder 56 of the main body 20 to engage the jam nut 50, placing residual locking forces between the top cap's external threaded portion 54 and the main body locking shoulder 56.

As stated, the threaded portion of the threaded top cap has a length greater than a depth of the actuating bore for forming an axial clearance therebetween; and the jam nut is axially threadably actuable along the threaded portion between an unlocked position wherein the jam nut is spaced above the main body; and a locked position wherein the jam nut engages the main body.

As shown in FIG. 3, the main body, the head 52 of the top cap 32 and the jam nut 50 are fit with respective flats 58 for opposing tool actuation.

In an embodiment, having reference to FIG. 4B and FIGS. 10A to 10B, the taper insert 28 has fluting 60. The fluting 60 enables elastic radial compression without plastic deformation. The fluting 60 is axial to permit elastic bending at each flute 60 without a permanent, plastic deformation while the axially extending slip-like portions retaining axial pulling design capability. Further, the taper insert 28 can be discontinuous about its circumference at a slot 62 extending axially therealong. The effective length or axial extent of the slot, open from a lower end, is compatible with the axial extent of engagement with the tapered bore to permit radial compression. As shown the slot 62 can extend axially along the entirely of the taper insert 28. The slot 62 enables a circumferential reduction of the gripping bore 30 upon compression, the gripping bore 30 closing radially in on, and gripping, the string end 6.

In embodiments, the gripping bore 30 is fit with horizontally or circumferentially extending wickers 64 for improving the gripping of the string end 6 therein in the gripping position.

As shown in FIGS. 4D and 9C, the jam nut 50, has internal threads 58 sized for movement along the externally threaded portion 54 of the top cap 32

As shown in FIGS. 5A and 5B, in the unactuated or open position, the taper insert's gripping bore 30 has a diameter for receiving the string end 6. The taper insert's driven shoulder 40 is standing axially proud inside the tapered bore 26, available for being driven axially downward into the tapered bore 26. The driving shoulder 42 of the top cap 32 is shown just engaged with the driven shoulder 40, poised for actuation. The jam nut 50 is in the unlocked position.

Having reference to FIG. 6, the main body is shown partially cut-away for illustrating the taper insert 28 residing within the tapered bore 26. The externally threaded portion 54 of the top cap 32 is only partially engaged with the internal threaded bore 34 of the main body 20, the taper insert 28 residing loosely within the tapered bore 26.

Procedure:

In an embodiment, typical capacity of a pulling clamp for a 1⅛″ continuous or coiled rod is about 70,000 pull weight, having a narrow profile of about 2⅞″ and a height of just under 7″. The top cap 32 is provided with a standard box end being the internal threaded pulling bore 37 compatible with conventional 1″ sucker rod.

With reference to FIG. 1A, and FIGS. 12A through 14C, a typical procedure is set forth for connecting a pulling clamp 10 according to embodiments disclosed herein to a string end 6 for lifting and lowering a continuous rod string 2, such as that extending through a top drive 1, such as for servicing the string 2 or a wellbore tool 100 such as a pump connected thereto. Similar techniques and adaptations are made for servicing a coiled tubing installation, an example of which is set forth in FIG. 15, wherein a string end 6 of the coiled tubing string 2 extends above the wellhead 4.

Good practice would suggest first cleaning and filing any sharp edges from the string end 6 prior to engagement with the pulling clamp 10. Emery paper can be used to clean any rust or protective shellac from the string end 6.

The string end 6 is measured and marked at about 2.5″ from the end. The jam nut 50 and top cap 32 of the pulling clamp 10 are unthreaded or backed off sufficient to remove any force on the taper insert 28, ensuring the taper insert 28 is in the receiving position.

In an embodiment, a tapered interface of about 7° is provided over about 2 inches axially. In this dimensional example, an axial actuation of about 0.06 inches is sufficient to effect gripping of the 1.125 inch cross-section.

Clamping the Tool:

Having reference to FIGS. 12A and 12B, in a first step the pulling clamp 10 is lowered onto the string end 6 by lowering the open string receiving bore 22 of the main body 20 over the string end 6, until the string end 6 is through the taper insert 28, such as by bottoming out against the driving shoulder 42 or a recess in the top cap 32. As a guideline, the 2.5″ mark should be covered or hidden within the main body 20. The top cap 32 is threaded into the main body 20 for engaging the driving shoulder 42 with the taper insert driven shoulder 40.

In a second step, as shown in FIGS. 13A, 13B and fancifully in FIG. 13C to illustrate the use of two wrenches 70 applied to the wrench flats 58 of the main body 20 and the top cap 32, at approximately 250 ft lbs torque, to thread the top cap 32 into the main body 20. The taper insert 28 is driven downwardly and the wickers 64 are driven or compressed radially inwardly to engage and grip the string end 6. The circumference of the taper insert 28 reduces and the axial slot 62 closes as the taper insert 28 is driven downwardly into the tapered bore 26. As the gripping bore 30 closes on the string end 6, the wrench torque rises to a set point sufficient to achieve the pulling capacity.

In a third step, as shown in FIGS. 14A, 14B using a wrench 70 (FIG. 14C) applied to at least the wrench flats 58 of the jam nut 50 and where the connection to the continuous string 2 resists rotation of the main body 20, the jam nut 50 is threaded downwardly to engage the locking shoulder 56 of the main body 20.

Thereafter an integrity check of the installation is performed. Depending on the particular wellhead 4, the continuous rod 2 in the wellhead 4 is prepared for a pull test of the pulling clamp 10. If so provided, rod lock rams are closed about the rod string 2 and tightened in the order of about 800 ft-lb.

As shown in FIG. 1B, a rod elevator 12 can be engaged to an underside of the pulling clamp 10, the pulling claim acting as an upset of the prior art sucker rods. As shown in FIG. 1A, where wellhead clearances are confined, a first end of a pony rod 14, such as a 1″ rod, can first be threaded into the connection bore 37 of the top cap 32. A rod elevator 12 is engaged with a second upset end 16 of the pony rod 14.

In either engagement, lifting apparatus is connected to the elevator 12 and is actuated to carefully lift to raise the elevator 12 while watching a weight indicator to confirm the pulling clamp 10 is engaged. At least 10,000 lbs is pulled to confirm pulling clamp engagement. The elevator 12 is lowered but maintained in tension with no weight on the weight indicator. The rod lock rams are then opened after which the connected rod string 2 is ready to be raised or lowered.

Releasing the Tool:

The rod string 2 is supported in the wellhead 4, such as on the rod lock rams or drive clamp 8. The jam nut 50 is backed off. The top cap 32 is loosened. There is no need to remove the top cap 32 from the main body 20. The top of the pulling clamp 10, such as on the top cap 32, is tapped to separate the taper insert 28 from the main body 20 and separate the taper insert 28 from the string end 6. The pulling clamp 10 can then be removed from the rod string 2.

In the case where the taper insert 28 has wickers 64, the string end 6 may have scars such as ridging or scoring. To avoid damage to a stuffing box or other drive head components, emery paper or a fine grade file is used to remove any rod scars prior to drive head removal or installation. Generally, as a good practice, one should keep the pulling clamp 10 free of crude oil, sand and debris, and regularly remove the taper insert 28 and inspect for cracks or deformation. One would visually inspect the pulling clamp 10 for damage before every use and lubricate all threads with thread anti seize compound. 

1. A pulling clamp for connection to a blunt, uphole string end of a continuous string comprising: a main body having a lower pulling end and an upper pulled end, the main body having a clamp bore formed therethrough, the clamp bore comprising a string-receiving opening at the pulling end for receiving the string end, an actuating bore at the pulled end and a tapered bore therebetween; a taper insert having a compressible gripping bore; and a top cap engageable with the actuating bore, the top cap being axially movable between passive and active positions to actuate the taper insert between a first receiving position and second gripping position respectively, wherein in the first receiving position, the gripping bore receives the string end and is passively uncompressed thereabout; and in the second gripping position, the top cap axially engages the taper insert for driving the taper insert axially into the tapered bore for radially compressing the taper insert about the string end for actively gripping the string end therein.
 2. The pulling clamp of claim 1 wherein: the actuating bore is threaded; and the top cap is threaded for threading axially into and out of the pulled end of the main body between the passive and active positions.
 3. The pulling clamp of claim 1 wherein in the second gripping position the gripping bore is compressed to a gripping diameter smaller than a diameter of the received string end.
 4. The pulling clamp of claim 1 wherein the taper insert further comprises an upper driven shoulder and the top cap further comprises a lower driving shoulder, the lower driving shoulder engaging the upper driven shoulder upon axial movement of the top cap into the actuating bore for actuating the top cap and taper insert to the second gripping position.
 5. The pulling clamp of claim 1 wherein, in the second gripping position, the string-receiving opening has an effective diameter smaller than a combined diameter of the taper insert and the string end.
 6. The pulling clamp of claim 1 further comprising a lock releasably actuable between the top cap and the main body, for locking engagement between the driving shoulder of the top cap and the driven shoulder of the taper insert in the second gripping position.
 7. The pulling clamp of claim 2 further comprising a jam nut actuable between the top cap and the main body, for locking engagement between the driving shoulder of the top cap and the driven shoulder of the taper insert in the second gripping position.
 8. The pulling clamp of claim 7 wherein: a threaded portion of the threaded top cap has a length greater than a depth of the actuating bore for forming an axial clearance therebetween; and the jam nut is axially threadably actuable along the threaded portion between an unlocked position wherein the jam nut is spaced above the main body; and a locked position wherein the jam nut engages the main body.
 9. The pulling clamp of claim 1 wherein the taper insert has an elastic compressible range to permit the radial compression and a radial release between the first released position and second gripping position.
 10. The pulling clamp of claim 1 wherein the taper insert further comprises axial fluting along an effective extent to enable elastic radial compression without plastic deformation.
 11. The pulling clamp of claim 1 wherein the taper insert is discontinuous about a circumference at a slot extending axially therealong to enable circumferential reduction upon compression in the gripping position.
 12. The pulling clamp of claim 1 wherein the gripping bore of the taper insert further comprises a plurality of horizontally extending wickers for engaging the string end in the gripping position.
 13. The pulling clamp of claim 1 for use with a lifting apparatus, wherein the top cap further comprises: a pulling connection for engagement with the lifting apparatus when the top cap and taper insert are in the second gripping position, axial pulling load being transferred from the continuous rod through the taper insert, to the main body and through the top cap to the lifting apparatus.
 14. The pulling clamp of claim 13 wherein the pulling connection comprises: a pony rod connected at a first end to a free end of the pulling clamp and engaging the lifting apparatus at a second upset end.
 15. The pulling clamp of claim 14 wherein the first end of the pony rod is threaded for connection to a threaded bore in the top cap.
 16. The pulling clamp of claim 1 wherein the continuous string is connected at a downhole end to a downhole tool, the continuous string being rotatable for driving the downhole tool.
 17. The pulling clamp of claim 16 wherein the downhole tool is a progressive cavity pump.
 18. A pulling clamp for connection to a blunt, uphole string end of a continuous string comprising: a main body having a bore for releasably gripping the string end and a lower pulling end, the main body forming an upset, the pulling end engageable by pulling apparatus.
 19. The pulling clamp of claim 18 wherein the main body has an upper pulled end, the main body having a clamp bore formed therethrough, the clamp bore comprising a string-receiving opening at the pulling end for receiving the string end, an actuating bore at the pulled end and a tapered bore therebetween; a taper insert having a compressible gripping bore; and a top cap engageable with the actuating bore, the top cap being axially movable between passive and active positions to actuate the taper insert between a first receiving position and second gripping position respectively, wherein in the first receiving position, the gripping bore receives the string end and is passively uncompressed thereabout; and in the second gripping position, the top cap axially engages the taper insert for driving the taper insert axially into the tapered bore for radially compressing the taper insert about the string end for actively gripping the string end therein.
 20. The pulling clamp of claim 19 wherein: the actuating bore is threaded; and the top cap is threaded for threading axially into and out of the pulled end of the main body between the passive and active positions. 